The purpose of this study is to compare methods of body composition in a heterogeneous group of adult men and women, as measured by underwater weighing, dual energy X-ray absorptiometry, skin folds, and bioelectrical impedance analysis. A total of 50 adult (over 18 years of age) male and female volunteers will be recruited for the study over a five year period (3/1/96 - 2/28/2001). Since the study began approximately two years ago, a total of 25 volunteers have completed the study. We expect to recruit approximately 8 additional volunteers during each of the remaining three years. No preliminary analysis of the data on the first 25 volunteers has, as yet, been completed.